Substrate processing apparatus and electrode structure

ABSTRACT

A substrate processing apparatus capable of preventing the abnormal discharge from being generated on a substrate. A housing chamber houses the substrate. A mounting stage arranged in the housing chamber, is configured to enable the substrate to be mounted thereon. A disc-like electrode structure is connected to a high-frequency power supply, and connected to a gas supply apparatus via at least one gas supply system. The electrode structure has therein at least one buffer chamber and a plurality of connecting sections connected to the gas supply system. The buffer chamber is communicated with the inside of the housing chamber via a number of gas holes, and is communicated with the gas supply system via the plurality of connecting sections. The plurality of connecting sections for the buffer chamber are arranged on the circumference of a circle centering around the center of the electrode structure at equal intervals.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.13/617,665 filed Sep. 14, 2012. U.S. application Ser. No. 13/617,665 isa continuation of U.S. application Ser. No. 12/029,728, filed on Feb.12, 2008, the entire content of each are incorporated herein byreference. U.S. application Ser. No. 12/029,728 claims the benefit ofpriority under 119(e) of U.S. Provisional Application Ser. No.60/938,729, filed May 18, 2007, and claims the benefit of priority under35 U.S.C. 119 from Japanese Application No. 2007-061749 filed Mar. 12,2007.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a substrate processing apparatus and anelectrode structure, and more particularly to a substrate processingapparatus including an electrode structure which is connected to ahigh-frequency power supply and to a gas supply apparatus adapted tosupply processing gas.

2. Description of the Related Art

As a substrate processing apparatus 60 adapted to perform plasmaprocessing, for example, etching processing to a wafer W as a substrate,there is known, as shown in FIG. 6, an apparatus configured byincluding: a chamber 61 which houses the wafer W; a mounting stage 62which is arranged in the chamber 61 and on which the wafer W is mounted;and a disc-like shower head 63 which is arranged opposite to themounting stage 62, and which introduces processing gas into the chamber61. In the substrate processing apparatus 60, high-frequency powersupplies 64 and 65 are respectively connected to the mounting stage 62and the shower head 63, which also function as electrodes. Then, themounting stage 62 and the shower head 63 supply high-frequency power tothe inside of the chamber 61, so that an electric field is generated inthe chamber 61. The electric field generates plasma from the processinggas, so that the plasma performs plasma processing to the wafer W.

Meanwhile, in order to perform the plasma processing uniformly to thewafer W, it is necessary to make uniform the distribution of plasmadensity on the wafer W. However, in order to make uniform thedistribution of plasma density, it is necessary to make uniform thedistribution of the electric field. Thus, for example, as in thesubstrate processing apparatus 60, there has been developed a substrateprocessing apparatus 60 in which branching waveguides (power supplytubes) 66 connected to the high-frequency power supply 65 and connectedto the shower head 63 symmetrically around the center of the shower head63 are provided, to thereby make uniform the distribution of theelectric field (for example, see Japanese Patent Laid-Open PublicationNo. 8-325759).

Further, the distribution of plasma density is influenced by thedistribution of processing gas introduced from the shower head.Accordingly, it is known that as shown in FIG. 7, in an electrodestructure 70 of the substrate processing apparatus, two mutuallyseparated buffer chambers 72 a and 72 b are provided in a shower head71, and a gas supply apparatus (not shown) for supplying processing gasis connected to each of the buffer chambers 72 a and 72 b via separategas supply systems 73 a and 73 b, respectively, so as to control theflow rate of the processing gas in each of the gas supply systems 73 aand 73 b. In the electrode structure 70, each of the buffer chambers 72a and 72 b is communicated with the inside of the chamber which houses awafer, and the flow rate of the processing gas supplied to the inside ofthe buffer chambers 72 a and 72 b is controlled, so as to enable theshower head 71 to control the distribution of the processing gasintroduced into the chamber.

Note that in the electrode structure 70, connecting sections 74 a and 74b, which respectively connect the gas supply systems 73 a and 73 b tothe buffer chambers 72 a and 72 b, are arranged at the same angle withrespect to the center of the shower head 71, that is, in the same radialdirection.

However, when the etching processing is performed to the wafer W byusing the above described electrode structure 70 shown in FIG. 7, microabnormal discharge (arcing) has been sometimes generated on the wafer W.Specifically, the arcing has been generated at the positions symmetricalwith the positions at which the connecting sections 74 a and 74 b arearranged, with respect to the center of the shower head 71. The arcingmay destroy a wiring and an insulating film of the semiconductor devicewhich are formed on the wafer W, and hence it is necessary to preventthe generation of the arcing.

SUMMARY OF THE INVENTION

The present invention provides a substrate processing apparatus and anelectrode structure which are capable of preventing the abnormaldischarge from being generated on the substrate.

Accordingly, in a first aspect of the present invention, there isprovided a substrate processing apparatus comprising a housing chamberconfigured to house a disc-like substrate, a mounting stage arranged inthe housing chamber and configured to enable the substrate to be mountedthereon, a high-frequency power supply, a gas supply apparatusconfigured to supply processing gas, and a disc-like electrode structureconnected to the high-frequency power supply, and connected to the gassupply apparatus via at least one gas supply system, wherein theelectrode structure is arranged opposite to the mounting stage, and hastherein at least one buffer chamber and a plurality of connectingsections connected to the gas supply system, wherein the buffer chamberis communicated with the inside of the housing chamber via a number ofgas holes, and is communicated with the gas supply system via theplurality of connecting sections, and wherein the plurality ofconnecting sections for the buffer chamber are arranged on thecircumference of a circle centering around the center of the electrodestructure at equal intervals.

According to the first aspect of the present invention, in the eachbuffer chamber provided in the electrode structure connected to thehigh-frequency power supply, the plurality of connecting sectionsconnected to the at least one gas supply system are arranged on thecircumference of a circle centering around the center of the electrodestructure at equal intervals. This enables the processing gas to beuniformly supplied to the inside of the each buffer chamber, so that thedistribution of the processing gas introduced into the housing chambervia the each buffer chamber can be made uniform. Also, this enables thestructure of the electrode structure to be made symmetrical about thecenter of the electrode structure, so that the distribution of theelectric field generated in the housing chamber can be made uniform. Asa result, the distribution of plasma density on the substrate can bemade uniform, so that the generation of the abnormal discharge on thesubstrate can be prevented.

The first aspect of the present invention can provide a substrateprocessing apparatus, wherein the electrode structure has therein aplurality of buffer chambers, and wherein when the total number of theconnecting sections corresponding to all the buffer chambers is set ton, the each connecting section is arranged at each rotational angle of360°/n±3° around the center of the electrode structure.

According to the first aspect of the present invention, when the totalnumber of the connecting sections corresponding to all the bufferchambers is set to n, the each connecting section is arranged at eachrotational angle of 360°/n±3° about the center of the electrodestructure. Thereby, the distribution of the processing gas introducedinto the housing chamber via the each buffer chamber can be made moreuniform, and the structure of the electrode structure can be made moresymmetrical.

The first aspect of the present invention can provide a substrateprocessing apparatus, wherein the electrode structure is configured by aceiling electrode plate, a cooling plate, and an upper electrode bodywhich are stacked in this order from the side of the housing chamber,and the ceiling electrode plate, the cooling plate, and the upperelectrode body are made of a conductive material, and wherein theplurality of connecting sections are arranged on the upper electrodebody, and the upper electrode body is connected to the high-frequencypower supply.

According to the first aspect of the present invention, the plurality ofconnecting sections are arranged on the upper electrode body connectedto the high-frequency power supply, and hence the structure of the upperelectrode body to which the high-frequency power is supplied can be madesymmetrical. Thereby, the distribution of the electric field generatedin the housing chamber can be surely made uniform.

The first aspect of the present invention can provide a substrateprocessing apparatus, wherein at least a portion of the gas supplysystem, which portion is connected to the connecting section, is made ofan insulating material.

According to the first aspect of the present invention, at least aportion of the gas supply system, which portion is connected to theconnecting section, is made of an insulating material, and hence the gassupply system does not affect the distribution of the electric field.Thereby, the distribution of the electric field generated in the housingchamber can be more surely made uniform.

Accordingly, in a second aspect of the present invention, there isprovided an electrode structure provided in a substrate processingapparatus which includes a housing chamber configured to house adisc-like substrate, a mounting stage arranged in the housing chamberand configured to enable the substrate to be mounted thereon, ahigh-frequency power supply, and a gas supply apparatus configured tosupply processing gas, wherein the electrode structure has a disc-likeshape, and is connected to the high-frequency power supply, andconnected to the gas supply apparatus via at least one gas supplysystem, wherein the electrode structure is arranged opposite to themounting stage, and has therein at least one buffer chamber and aplurality of connecting sections connected to the gas supply system,wherein the each buffer chamber is communicated with the inside of thehousing chamber via a number of gas holes, and is communicated with thegas supply system via the plurality of connecting sections, and whereinthe plurality of connecting sections for the each buffer chamber arearranged on the circumference of a circle centering around the center ofthe electrode structure at equal intervals.

The features and advantages of the invention will become more apparentfrom the following detailed description taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view schematically showing a configuration of asubstrate processing apparatus according to an embodiment of the presentinvention.

FIG. 2 is a plan view schematically showing a positional relationbetween the shower head, the clamp, the central gas supply system, andthe peripheral gas supply system shown in FIG. 1.

FIG. 3 is a sectional view schematically showing a configuration of avariation of the electrode structure according to the presentembodiment.

FIG. 4A and FIG. 4B are graphs showing the etching rate distribution atthe time when etching processing is performed to an oxide film on awafer by using the substrate processing apparatus according to thepresent embodiment and a conventional substrate processing apparatus:FIG. 4A shows the etching rate distribution at the time when theconventional substrate processing apparatus is used; and FIG. 4B showsthe etching rate distribution at the time when the substrate processingapparatus according to the present embodiment is used.

FIG. 5A and FIG. 5B are graphs showing the etching rate distribution atthe time when etching processing is performed to a photoresist film onthe wafer by using the substrate processing apparatus according to thepresent embodiment and the conventional substrate processing apparatus:FIG. 5A shows the etching rate distribution at the time when theconventional substrate processing apparatus is used; and FIG. 5B showsthe etching rate distribution at the time when the substrate processingapparatus according to the present embodiment is used.

FIG. 6 is a sectional view schematically showing a configuration of theconventional substrate processing apparatus.

FIG. 7 is a plan view schematically showing a configuration of theconventional electrode structure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, embodiments according to the present invention will bedescribed with reference to the accompanying drawings.

First, a substrate processing apparatus according to an embodiment ofthe present invention will be described.

FIG. 1 is a sectional view schematically showing a configuration of asubstrate processing apparatus according to an embodiment of the presentinvention. The substrate processing apparatus is configured such thatetching processing as plasma processing is performed to a semiconductorwafer as a substrate.

In FIG. 1, the substrate processing apparatus 10 has, for example, achamber 11 (housing chamber) which houses a disc-like semiconductorwafer (hereinafter referred to as simply “wafer”) W having a diameter of300 mm. A cylindrical susceptor supporting stage 12 is arranged on thebottom surface inside the chamber 11, and a cylindrical susceptor 13(mounting stage) is arranged on the susceptor supporting stage 12.

An ESC (Electrostatic Chuck) 14 (mounting stage) is arranged on thesusceptor 13. The ESC 14 is made of, for example, aluminum. A ceramicmaterial such as alumina, or the like, is thermally sprayed onto theupper surface of the ESC 14 to form a thermally sprayed film (notshown). In the thermally sprayed film, there is provided anelectrostatic electrode plate 16 to which a DC power supply 15 iselectrically connected.

The wafer W housed in the chamber 11 is mounted on the upper surface(hereinafter referred to as “mounting surface”) of the ESC 14. When apositive DC voltage is applied to the electrostatic electrode plate 16from the DC power supply 15, a negative potential is generated in thecontact surface of the wafer W in contact with the mounting surface, tocause a potential difference between the electrostatic electrode plate16 and the contact surface of the wafer W. As a result, the wafer W isattracted to be held on the mounting surface of the ESC 14 by theCoulomb force or Johnson Rahbeck force resulting from the potentialdifference.

A plurality of heat transfer gas supply holes 17 are opened in themounting surface of the ESC14. The plurality of heat transfer gas supplyholes 17 are connected to a heat transfer gas supply section (not shown)via a heat transfer gas supply line 18. The heat transfer gas supplysection supplies helium (He) gas as the heat transfer gas between thecontact surface of the wafer W and the mounting surface via the heattransfer gas supply holes 17. The helium gas supplied to the gap betweenthe contact surface of the wafer W and the mounting surface effectivelytransfers the heat of the wafer W to the ESC 14.

The susceptor 13 is made of, for example, an aluminum alloy, and isconnected to a lower high-frequency power supply 19 via a lower matchingbox (Matcher) 20, and the lower high-frequency power supply 19 supplieshigh-frequency power of relatively low frequency to the susceptor 13.Thereby, the susceptor 13 functions as a lower electrode for supplyingthe high-frequency power to a processing space S which is a spacebetween the susceptor 13 and a shower head 24 as will be describedbelow. Further, the lower matching box 20 matches the internal impedanceof the lower high-frequency power supply 19 with a load impedance.

Inside the susceptor supporting stage 12, for example, there is providedan annular coolant chamber 21 extending in the circumferentialdirection. To the coolant chamber 21, low-temperature coolant such as,for example, cooling water and Galden (registered trademark) fluid iscirculated and supplied via a coolant pipe 22 from a chiller unit (notshown). The susceptor supporting stage 12 cooled by the low-temperaturecoolant cools the wafer W via the ESC 14.

Further, an annular focus ring 23 is arranged on the ESC 14. The focusring 23 is made of a conductive material such as, for example, silicon,and surrounds the wafer W which is attracted to be held on the mountingsurface of the ESC 14. Further, the focus ring 23 converges plasmagenerated in the processing space S to the surface of the wafer W, tothereby improve the efficiency of the etching processing.

The disc-like shower head 24 (electrode structure) is arranged in theceiling section of the chamber 11, so as to face the wafer W mounted onthe ESC 14. The shower head 24 has a ceiling electrode plate 25, acooling plate 26, and an upper electrode supporting body 27 (upperelectrode body) which are stacked in this order from the side of theprocessing space S. An upper high-frequency power supply 30 is connectedto the upper electrode supporting body 27 via a power supply tube 28 andan upper matching box 29. The upper high-frequency power supply 30supplies high-frequency power of a relatively high frequency to theupper electrode supporting body 27. The ceiling electrode plate 25, thecooling plate 26, and the upper electrode supporting body 27 are made ofa conductive material such as, for example, an aluminum alloy, and hencethe high-frequency power supplied to the upper electrode supporting body27 is supplied to the processing space S via the cooling plate 26 andthe ceiling electrode plate 25. That is, the shower head 24 functions asan upper electrode for supplying the high-frequency power to theprocessing space S. Note that the function of the upper matching box 29is the same as the function of the above described lower matching box20.

Note that the outer periphery of the shower head 24 is covered by anannular dielectric member 31 which insulates the shower head 24 from thewall of the chamber 11. Further, the outside of the power supply tube 28is covered by a case-shaped grounding conductive member 32, and thepower supply tube 28 penetrates the upper-surface central portion of thegrounding conductive member 32. In the penetrating section, aninsulating member 33 is provided between the grounding conductive member32 and the power supply tube 28.

Further, in the shower head 24, the cooling plate 26 has, in the insidethereof, a central buffer chamber 34 formed of a disc-like spacecentering on the center (hereinafter referred to as “shower headcenter”) of the shower head 24, and a peripheral buffer chamber 35formed of an annular space concentric with the central buffer chamber34. The central buffer chamber 34 and the peripheral buffer chamber 35are separated by an annular partition wall member such as, for example,an O ring 37. Further, the cooling plate 26 and the ceiling electrodeplate 25 have a number of penetrating gas holes 36 through which thecentral buffer chamber 34 and the peripheral buffer chamber 35 arecommunicated with the processing space S.

Further, in the shower head 24, a plurality of clamps 38 and 40(connecting sections) made of a conductive material such as, forexample, aluminum are arranged on the upper electrode supporting body27. Specifically, two clamps 38 are arranged at positions correspondingto the central buffer chamber 34, and two clamps 40 are arranged atpositions corresponding to the peripheral buffer chamber 35. The twoclamps 38 are connected to a central gas supply system 39 consisting oftwo branched pipes. The two clamps 40 are connected to a peripheral gassupply system 41 consisting of two branched pipes. Note that in thecentral gas supply system 39 and the peripheral gas supply system 41,the portions respectively connected to the clamps 38 and 40,specifically, the portions existing in the inside of the groundingconductive member 32, are made of an insulating material, specifically,a resin.

The central buffer chamber 34 is communicated with the central gassupply system 39 via the two clamps 38, and the peripheral bufferchamber 35 is communicated with the peripheral gas supply system 41 viathe two clamps 40. Note that the central gas supply system 39 and theperipheral gas supply system 41 are connected to a branch flow rateadjusting apparatus 42 which adjusts the flow rates of the mixture ofprocessing gas and additional gas to the central gas supply system 39and the peripheral gas supply system 41, respectively. The branch flowrate adjusting apparatus 42 is connected to a processing gas supplyapparatus for supplying the processing gas, and to an additional gassupply apparatus for supplying the additional gas (both not shown). Notethat the processing gas in the present embodiment corresponds to, forexample, CF-based gas and oxygen gas, and the additional gas correspondsto, for example, argon gas.

In the shower head 24, the mixed gas containing the processing gas isintroduced into the central buffer chamber 34 and the peripheral bufferchamber 35 from the branch flow rate adjusting apparatus 42 via thecentral gas supply system 39 and the peripheral gas supply system 41.The introduced mixed gas is introduced into the processing space S via anumber of the penetrating gas holes 36. Therefore, the shower head 24functions as a gas introducing device. Further, in the shower head 24, acoolant chamber (not shown) is provided in the cooling plate 26. Acoolant such as, for example, cooling water and Galden (registeredtrademark) fluid introduced from coolant introducing sections 43 a and43 b as will be described below, is supplied to the inside of thecoolant chamber. The cooling plate 26 cools the mixed gas introducedinto the central buffer chamber 34 and the peripheral buffer chamber 35by the coolant in the coolant chamber.

In the present embodiment, the mixed gas introduced from the penetratinggas holes 36 corresponding to the peripheral buffer chamber 35 isdistribution-diffused toward the periphery of the wafer W mounted on themounting surface, and the mixed gas introduced from the penetrating gasholes 36 corresponding to the central buffer chamber 34 isdistribution-diffused toward the central portion of the wafer W mountedon the mounting surface. Note that the density distribution of the mixedgas on the wafer W can be adjusted by adjusting the flow rate of themixed gas which is distributed to each of the central gas supply system39 and the peripheral gas supply system 41 by the branch flow rateadjusting apparatus 42.

FIG. 2 is a plan view schematically showing a positional relationbetween the shower head, the clamps, the central gas supply system, andthe peripheral gas supply system, which are shown in FIG. 1.

In FIG. 2, the two clamps 38 corresponding to the central buffer chamber34 are arranged on the circumference of a circle centering around theshower head center at equal intervals, specifically, at each 180°±3°.Further, the central buffer chamber 34 is formed of a disc-like spacecentering on the shower head center. Therefore, in the central bufferchamber 34, the mixed gas is introduced symmetrically around the showerhead center. As a result, the mixed gas can be uniformly supplied intothe central buffer chamber 34.

Further, the two clamps 40 corresponding to the peripheral bufferchamber 35 are also arranged on the circumference of a circle centeringaround the shower head center at equal intervals, specifically, at each180°±3°. The peripheral buffer chamber 35 is formed of an annular spacecentering around the shower head center. Therefore, also in theperipheral buffer chamber 35, the mixed gas is introduced symmetricallyaround the shower head center. As a result, the mixed gas can beuniformly supplied to the inside of the peripheral buffer chamber 35.

Further, in the shower head 24, the total number of the clamps 38 and 40is four, and each of the clamps 38 and 40 is arranged at each rotationalangle of 360°/4±3° in the rotational system centering around the showerhead center. Specifically, the rotational angle between the adjacentclamps 38 and 40, which angle centers around the shower head center, is90°±3°. Thereby, the mixed gas can be symmetrically introduced into theprocessing space S via the central buffer chamber 34 and the peripheralbuffer chamber 35. Therefore, the distribution of the mixed gasintroduced into the processing space S can be made more uniform.

Note that in the shower head 24, the coolant introducing sections 43 aand 43 b, and a PT sensor 44 which is a temperature measuring sensor,are arranged so as to avoid the clamps 38 and 40, the central gas supplysystem 39, and the peripheral gas supply system 41.

Returning to FIG. 1, in the substrate processing apparatus 10, a highpass filter 45 is electrically connected to the susceptor 13, and thehigh pass filter 45 passes the high-frequency power from the upperhigh-frequency power supply 30 to the ground. Further, a low pass filter46 is electrically connected to the shower head 24, and the low passfilter 46 passes the high-frequency power from the lower high-frequencypower supply 19 to the ground.

Further, in the substrate processing apparatus 10, a flow path, throughwhich the gas above the ESC 14 is discharged to the outside of thechamber 11, is formed between the inside wall of the chamber 11 and theside surface of the ESC 14 (susceptor 13), and an exhaust plate 47 isarranged in the middle of the flow path. The exhaust plate 47 is aplate-shaped member having a number of holes, and captures or reflectsthe plasma generated in the processing space S, so as to prevent theleakage of the plasma.

In the substrate processing apparatus 10, when the mixed gas isintroduced into the processing space S from the shower head 24, and whenthe high-frequency power is supplied to the processing space S from thesusceptor 13 and the shower head 24, a high frequency electric field isgenerated in the processing space S, so that the processing gas in themixed gas is excited to become plasma. The plasma performs etchingprocessing to the wafer W.

Note that the operation of each component of the above describedsubstrate processing apparatus 10 is controlled by a CPU of a controller(not shown) provided in the substrate processing apparatus 10 on thebasis of a program corresponding to the etching processing.

According to the substrate processing apparatus 10 of the presentembodiment, the two clamps 38 corresponding to the central bufferchamber 34 and connected to the central gas supply system 39 arearranged on the circumference of a circle centering around the showerhead center at equal intervals. Further, the two clamps 40 correspondingto the peripheral buffer chamber 35 and connected to the peripheral gassupply system 41 are arranged on the circumference of a circle centeringaround the shower head center at equal intervals. Thereby, theprocessing gas can be uniformly supplied into the central buffer chamber34 and the peripheral buffer chamber 35, so that it is possible to makeuniform the distribution of the processing gas introduced into theprocessing space S via the central buffer chamber 34 and the peripheralbuffer chamber 35. Further, the structure of the shower head 24 whichsupplies high-frequency power to the processing space S can be madesymmetrical with respect to the shower head center, so that it ispossible to make uniform the distribution of the electric fieldgenerated in the processing space S. As a result, the distribution ofthe density of plasma generated on the wafer W can be made uniform, sothat it is possible to prevent the generation of arcing on the wafer W.

In the above described substrate processing apparatus 10, the totalnumber of the clamps 38 and 40 is four, and hence the clamps 38 and 40are arranged at each rotational angle of 90°±3° around the shower headcenter. Therefore, the distribution of the processing gas introducedinto the processing space S can be made more uniform. Further, thestructure of the shower head 24 can be made more symmetrical withrespect to the shower head center.

Further, in the above described substrate processing apparatus 10, thefour clamps 38 and 40 are arranged on the upper electrode supportingbody 27 connected to the upper high-frequency power supply 30, and hencethe structure formed by the upper electrode supporting body 27 to whichthe high-frequency power is supplied, and formed by the four clamps 38and 40 can be made symmetrical. Thereby, the distribution of theelectric field generated in the processing space S can be surely madeuniform.

Further, in the above described substrate processing apparatus 10, theportions of the central gas supply system 39 and the peripheral gassupply system 41, which portions are respectively connected to theclamps 38 and 40, are made of a resin, and hence the high-frequencypower supplied to the upper electrode supporting body 27 is preventedfrom being transmitted to the central gas supply system 39 and theperipheral gas supply system 41 via the clamps 38 and 40. Therefore, thecentral gas supply system 39 and the peripheral gas supply system 41 donot affect the distribution of the electric field in the processingspace S, so that the distribution of the electric field generated in theprocessing space S can be more surely made uniform.

In the above described embodiment, two clamps are arranged on the upperelectrode supporting body 27 in correspondence with each of the bufferchambers, but the number of the clamps arranged in correspondence witheach of the buffer chambers is not limited to two. For example, thenumber of the clamps may be three or more. In this case, N clampscorresponding to each of the buffer chambers are arranged on thecircumference of a circle centering around the shower head center atequal intervals, specifically, at each 360°/N.

Further, the number of the buffer chambers provided in the shower head24 is not limited to two, but the number of the buffer chambers may beone, or three or more. Even in this case, when the total number of theclamps arranged on the upper electrode supporting body 27 is set to n,the clamps are arranged at each rotational angle of 360°/n±3° in therotational system centering around the shower head center. For example,as shown in FIG. 3, when the shower head 24 has three buffer chambers,and when the number of the clamps arranged on the upper electrodesupporting body 27 in correspondence with each of the buffer chambers istwo, the total number of the clamps is 6, and hence the clamps arearranged at each rotational angle of 60°±3° in the rotational systemcentering around the shower head center.

Further, in the above described embodiment, the coolant introducingsections 43 a and 43 b are not symmetrically arranged with respect tothe shower head center. However, in the upper electrode supporting body27, the two coolant introducing sections may be symmetrically arranged.Specifically, the two coolant introducing sections may be arranged atequal intervals on the circumference of a circle centering around theshower head center, for example, at each 180°±3°. Thereby, the structureof the shower head 24 can be made still more symmetrical about theshower head center, so that the distribution of the electric fieldgenerated in the processing space S can be surely made uniform. Further,the plurality of components arranged on the upper electrode supportingbody 27 may be preferably arranged as symmetrically as possible withrespect to the shower head center.

Note that in the above described embodiment, the location tolerance inthe arrangement of the clamps and the like is set to ±3°. However, thegeneral machining tolerance is also in general ±3°, and hence specialtolerance management to realize the above described arrangement of theclamps and the like is not needed. Thereby, it is possible to preventthe increase in manufacturing cost of the shower head 24.

EXAMPLE

Next, an example according to the present invention will be specificallydescribed.

Example

First, when it was observed whether or not arcing was generated on awafer W during the etching processing performed to the wafer W in thesubstrate processing apparatus 10, the generation of the arcing was notobserved. Further, when the charge distribution on the surface of thewafer W was investigated, it was confirmed that the charges weredistributed in the state of concentric circles, and that unevendistribution of the charges in the circumferential direction was notgenerated.

Further, the etching processing was performed to the oxide film on thewafer W in the substrate processing apparatus 10, and the distributionof etching rate at this time was observed. The observation result isshown in the graph of FIG. 4B. Further, the etching processing wasperformed to the photoresist film on the wafer W in the substrateprocessing apparatus 10, and the distribution of etching rate at thistime was observed. The observation result is shown in the graph of FIG.5B.

Comparison Example

First, when it was observed whether or not arcing was generated on awafer W during the etching processing performed to the wafer W in thesubstrate processing apparatus (hereinafter referred to as “conventionalsubstrate processing apparatus”) provided with the electrode structure70 shown in FIG. 7, it was confirmed that the arcing was generated atpositions symmetrical with the positions at which the connectingsections 74 a and 74 b are arranged, with respect to the center of theshower head 71. Further, when the charge distribution on the surface ofthe wafer W was investigated, it was confirmed that uneven distributionof the charges was generated at positions symmetrical with the positionsat which the connecting sections 74 a and 74 b are arranged, withrespect to the center of the shower head 71.

Further, the etching processing was performed to the oxide film on thewafer W in the conventional substrate processing apparatus, thedistribution of etching rate at this time was observed. The observationresult is shown in the graph of FIG. 4A. Further, the etching processingwas performed to the photoresist film on the wafer W in the conventionalsubstrate processing apparatus, the distribution of etching rate at thistime was observed. The observation result is shown in the graph of FIG.5A.

By comparing Example with Comparison Example, it was seen that inComparison Example, the arcing was generated, and the unevendistribution of the charges was also generated, while in Example, thearcing was not generated, and also the uneven distribution of thecharges was not generated. From this fact, it was seen that in Example,the distribution of the processing gas introduced into the processingspace S was made uniform, and the distribution of the electric fieldgenerated in the processing space S was also made uniform, as a resultof which the distribution of the density of plasma generated on thewafer W was made uniform.

In addition, the graph of FIG. 4A was compared with the graph of FIG.4B, and further the graph of FIG. 5A was compared with the graph of FIG.5B. As a result, it was seen that in any of the etching processing ofthe oxide film and the etching processing of the photoresist film, thedispersion in the distribution of etching rate in Example is smallerthan the dispersion in the distribution of etching rate in ComparisonExample. Also from this fact, it was seen that in Example, thedistribution of the density of plasma generated on the wafer W was madeuniform.

1. A substrate processing apparatus comprising: a chamber that houses adisk-shaped substrate; a first electrode that is arranged in thechamber, the substrate being mounted on the first electrode; a secondelectrode constituting a shower head that is arranged such as to facethe mounted substrate and has a number of penetrating gas holes, thesecond electrode has therein a space; a high-frequency power source thatsupplies high-frequency power between the first and second electrodes; acentral vacancy that is comprised of a central portion of the space inthe shower head; at least two annular buffer vacancies that arecomprised of annular spaces formed outside the central vacancy andarranged sequentially in a radial direction of the shower head; aplurality of annular partition wall members that divide the space in theshower head with respect to the radial direction of the shower head suchas to form the central vacancy and the at least two annular buffervacancies; a plurality of pipes that are connected respectively to thecentral vacancy and the at least two annular buffer vacancies such as tosupply processing gas and additional gas respectively to the centralvacancy and the at least two annular buffer vacancies; and a branch flowrate adjusting apparatus that adjusts a flow rate of the processing gaswhich flow through each of the plurality of pipes; wherein each of theplurality of pipes is branched into at least two branched pipes, and thebranched pipes are connected to each of the central vacancy and the atleast two annular buffer vacancies via at least two connecting sectionswhich are disposed on each of the central vacancy and the at least twoannular buffer vacancies along a circumference of a circle arrangedthereon at equal intervals, the at least two connecting sectionsbelonging to each of the central vacancy and the at least two annularbuffer vacancies are disposed symmetrically around the shower headcenter, regarding all the connecting sections of the plurality of pipes,one connecting section is shifted from another connecting sectionadjacent thereto at constant degrees in a rotational system centeringaround the center of the shower head, whereby a mixture of theprocessing gas and the additional gas is supplied symmetrically withrespect to the center of the shower head and uniformly into the chamberso as to make uniform the distribution of an electric field generated ina processing space inside the chamber.
 2. A substrate processingapparatus as claimed in claim 1, wherein the shower head is configuredby a ceiling electrode plate, a cooling plate, and an upper electrodebody which are stacked in this order from the side of the processingspace of the chamber, and the ceiling electrode plate, the coolingplate, and the upper electrode body are made of a conductive material.3. A substrate processing apparatus as claimed in claim 2, wherein thecooling plate has a coolant chamber therein and at least two coolantintroducing sections from which a coolant is supplied to the coolantchamber, and the coolant introducing sections are arranged symmetricallywith respect to the center of the shower head.
 4. A substrate processingapparatus as claimed in claim 1, wherein the high-frequency power sourceis connected to the first electrode.
 5. A substrate processing apparatusas claimed in claim 1, wherein the outside of a power supply tube whichis directly connected to a central portion of the shower head is coveredby a case-shaped grounding conductive member, and portions of theplurality of pipes existing in the inside of the grounding conductivemember are made of an insulating material.
 6. A substrate processingapparatus as claimed in claim 5, wherein the portions of the pluralityof pipes existing in the inside of the grounding conductive member aremade of a resin.
 7. A substrate processing apparatus as claimed in claim1, when the total number of all the connecting sections is set to n,each of all the connecting sections is arranged at each rotational angleof 360°/n±3° in the rotational system centering around the center of theshower head.